Rabbi Abba bar Kahana, in the name of Rabbi Yehudah ben Pazzi, derived this from the following statement: Rabbi Tarfon said, “I was once on the road, and I halted and reclined to recite the Shema, following the rule of Bet Shammai,
and exposed myself to danger from robbers (Berachot 10b).” You see therefore, that if he had not recited the Shema at all he would only have transgressed a positive commandment, but now that he did say it, he rendered his life forfeit. This shows that the words of the Scribes are more beloved than those of the Torah. (Shir Hashirim Rabbah 1.2.2:1)

Rabbi Abba holds that we can only properly observe the laws of the Torah according to the guidelines of the Sages. The Mitzvot do not have value without the Sages instructions. It is their teachings that empower the Mitzvah.

The power of the Oral Law, our study of Torah, actually affects the power of our observance of the Mitzvot of the Torah. This is why our Torah study is essential to our observance of the Mitzvot.